Year	% of total energy
1960	1.7737820069319996
1961	1.6633955011497124
1962	1.5100817314859365
1963	1.3940012109826327
1964	1.287134366633228
1965	1.2428389148165708
1966	1.2029354636122898
1967	1.1074418064533091
1968	0.9919885759346712
1969	0.9101541432300038
1970	2.4326112304526175
1971	2.3441129360661432
1972	2.2355371995992197
1973	2.0958143656968065
1974	2.200405272404936
1975	2.2601851384337315
1976	2.061806177822232
1977	2.089221492650565
1978	2.074012699689673
1979	2.0646986018737707
1980	2.1207567569512995
1981	2.216093440535908
1982	2.3318861138837446
1983	2.444544994782463
1984	2.480167325141608
1985	2.528539500895092
1986	2.44322728724699
1987	2.4626622550790382
1988	2.5370632335360837
1989	2.8575903827735876
1990	2.660157962122271
1991	2.724606325569901
1992	2.7182496405227874
1993	2.747160101310967
1994	2.6986893161968957
1995	2.678343965717292
1996	2.712679907762144
1997	2.819124492582568
1998	2.8316666438272873
1999	2.8460682718775483
2000	2.8485695154496065
2001	2.8381918641562134
2002	2.9259364399565584
2003	3.1791660798299968
2004	3.1806314887051146
2005	3.465616489625723
2006	3.705011629696358
2007	4.113383853409304
2008	4.362880604965173
2009	4.835840481232255
2010	5.03231137885523
2011	4.866186539879536
2012	5.296725272106874
2013	5.355376997020192
2014	5.42732955682574
2015	5.450773281751896